Nonmonotonic Energy Dependence of Net-Proton Number Fluctuations

Nonmonotonic variation with collision energy (root s(NN)) of the moments of the net-baryon number distribution in heavy-ion collisions, related to the correlation length and the susceptibilities of the system, is suggested as a signature for the quantum chromodynamics critical point. We report the first evidence of a nonmonotonic variation in the kurtosis times variance of the net-proton number (proxy for net-baryon number) distribution as a function of root s(NN) with 3.1 sigma significance for head-on (central) gold-on-gold (Au + Au) collisions measured solenoidal tracker at Relativistic Heavy Ion Collider. Data in noncentral Au + Au collisions and models of heavy-ion collisions without a critical point show a monotonic variation as a function of root s(NN.)

Automated summary

The nonmonotonic variation in the kurtosis times variance of the net-proton number distribution with increasing collision energy suggests a possible signature for the quantum chromodynamics critical point. This evidence was observed in central gold-on-gold collisions at the Relativistic Heavy Ion Collider, while noncentral collisions and models without a critical point exhibit monotonic variations.